Preparation of bilayer laminate and preformed sheet for use therein

ABSTRACT

Preformed, energy-absorbing, scratch resistant, optical, flexible, and self-healing polyurethane sheets, which are adhesive under the influence of heat and pressure; bilayer glazing laminates and bilayer safety windshields including said sheets; wherein said polyurethane sheet is prepared preferably by reactive-casting on a horizontal support and formed preferably from a polyisocyanate monomer including about 2 to about 10 wt. % of urea groups.

This is a division of application Ser. No. 629,251, filed July 10, 1984.

FIELD OF THE INVENTION

The present invention relates to a preformed sheet of energy-absorbing,adhesive, and scratch resistant plastic material, and to a glazinglaminate including said sheet and methods and compositions useful forthe preparation of said sheet and laminate. This invention relates alsoto a bilayer laminate having improved moisture resistant,energy-absorbing, optical and scratch resistant properties and, inparticular, to an improved vehicle windshield including an inner exposedply of scratch resistant, anti-lacerative plastic material.

REPORTED DEVELOPMENTS

The patent literature extending over a period of almost half a centuryreveals numerous efforts to fabricate a bilayer laminate which is usefulas a vehicle safety windshield and which comprises a single ply of glassand a ply of energy-absorbing, mar-resistant plastic material. That theproducts of such attempts have not been entirely satisfactory isevidenced by the present unavailability of a commercially acceptablebilayer windshield.

Bilayer laminates are disclosed in U.S. Pat. Nos. 3,808,077; 3,881,043;3,900,686; 4,041,208; 4,085,092; 4,109,055; 4,139,764; and 4,039,720;and in the following copending U.S. applications, each of which isassigned to the same assignee as the present application, Ser. Nos.213,225; 274,547; and 579,035. Invariably the plastic ply of the bilayerlaminates disclosed therein have one or more desirable properties, suchas energy absorption, optical clarity, or chemical resistance, but areeither impractical to manufacture and/or deficient in one or more otherproperties, such as, for example, adhesive strength, mar-resistance, ormoisture sensitivity. For example, bilayer laminates comprising a singleplastic ply having acceptable scratch resistant properties suffer from adecided lack of energy-absorbing and adhesive properties, while thosebilayer laminates having acceptable energy-absorbing properties sufferfrom a decided lack of scratch resistance and a lack of adhesiveproperties. The prior art has dealt with some of these shortcomings suchas insufficient adhesive strength by utilizing an adhesion promoter orseparate adhesive layer, while the deficiencies such as inadequatescratch resistance have been approached by providing a separate surfacetreatment such as a hard or soft scratch resistant coating or byproviding a two-ply plastic sheet which combines the desirableproperties of two materials in one ply. However, these approaches havealso encountered problems, such as deficiencies in one or more otherproperties including optical clarity.

Many plastics, including polyvinyls, polycarbonates, and polyurethanes,have been proposed for use in bilayer laminates. Polyurethanes have beenwidely used as both an exposed ply and as an interlayer sandwichedbetween two sheets of glass or plastic. Various types of polyurethaneshave been described for such glazing uses in the patents andapplications mentioned above, as well as in U.S. Pat. Nos. 3,509,015,3,620,905, and 4,241,140, but they do not possess to the desired extentall of the properties that are needed in a plastic sheet for use in asuccessful bilayer windshield.

The present invention relates to an improved polyurethane sheet which isparticularly useful for preparing a bilayer glazing laminate as theresult of its possessing a combination of properties that are requiredin this type of safety product.

SUMMARY OF THE INVENTION

The present invention relates to a preformed transparent sheet havingoptical properties and comprising an energy-absorbing polyurethane ply,characterized in that said polyurethane ply is prepared by reactivecasting on a level, horizontal support, a reaction mixture including: anisocyanate component, having a viscosity of less than 5000 mPaS at 40°C., and comprising an aliphatic diisocyanate, a cycloaliphaticdiisocyanate or an isocyanate prepolymer; and, a polyol componentcomprising a polymeric diol having a molecular weight (hereinafter "MW")of about 500 to about 4000, and a short chain diol.

The present invention relates also to a preformed flexible transparentsheet, effective for use in a glazing laminate and having optical,moisture resistant, and energy-absorbing properties and comprisingpolyurethane which is substantially non-tacky at room temperature, butwhich is capable of itself being adhesive under the influence of heatand pressure, said sheet characterized in that, as an exposed ply in aglazing laminate, it is capable of maintaining, in the absence of anadhesion promoter, effective adhesion, as measured by the temperatureand moisture conditions of Test Nos. 3 and 4, American Standard SafetyCode for Safety Glazing Materials for Glazing Motor Vehicles Operatingon Land Highways, Revision Z 26.1--1966 (hereinafter "ANSI-Z26").

This invention relates also to a method for the preparation of apreformed flexible, transparent polyurethane sheet of the type describedabove comprising:

(1) forming on a horizontal support a liquid film comprising a mixtureof monomers and a polyurethane-forming catalyst;

(2) maintaining said liquid film at a temperature and for a timesufficient to permit the formation of a uniformly thick and level liquidfilm;

(3) raising the temperature of said uniformly thick and level liquidfilm and maintaining the film at an elevated temperature sufficient tofully polymerize the film into a solid polyurethane sheet within lessthan about one hour while it is positioned on said horizontal support.

Another aspect of the present invention relates to a composition whichis liquid at a temperature greater than about 25° C. and which exhibitsa viscosity at about 35° to about 45° C. sufficient to permit theformation on a horizontal support of a uniformly thick and level filmthereof, and comprising a solvent-free mixture which is capable offorming a solid polyurethane upon heating, and which comprises:

(A) a cycloaliphatic polyisocyanate component including about 2 to about10 wt. % of urea groups and about 30 to about 33 wt. % of NCO groups;

(B) a polyol component including:

(1) about 30 to about 45 OH equivalent percent of a polymeric diolhaving a MW of about 500 to about 3000;

(2) about 20 to about 70 OH equivalent percent of a chain extender diol;and

(3) about 0 to about 35 OH equivalent percent of a polyol with an OHfunctionality greater than two; and

(C) a polyurethane-forming catalyst;

wherein the NCO/OH ratio of said mixture is about 0.8:1 to about 1:1.

A further aspect of the present invention relates to a glazing laminatecomprising a glass or plastic sheet and a preformed transparentenergy-absorbing plastic ply having surface properties including ascratch resistance of greater than 20 g as measured by the Erichsen 413apparatus and an abrasion resistance of less than 4% haze as measuredaccording to ECE Regulation No. 43.

A particular aspect of the present invention relates to a bilayerglazing laminate which exhibits optical, energy-absorbing, moisture andtemperature resistant, and abrasion resistant properties as required byANSI-Z26, Test Nos. 1, 2, 3, 4, 9, 12, 17, 26, and 28, and whichcomprises a preformed sheet as described above adhered to a glass orrigid plastic ply.

Other aspects of the present invention, including methods for thepreparation of glazing laminates, are described herein.

DETAILED DESCRIPTION OF THE INVENTION

The term "adhesion promoter" means a material which, when added to apolyurethane solution or to the reaction mixture from which thepolyurethane is prepared, or when used to coat the surface of apolyurethane article, improves the strength and longevity of an adhesivebond including said polyurethane. Exemplary adhesion promoters includealkoxy silanes such as: gamma aminopropyl-triethoxysilane, sold as"A-1100" by Union Carbide Corp. or by Dow Corning as "Z-6020";andN-(beta-amino ethyl) gamma aminopropyl-trimethoxysilane sold by UnionCarbide Corp. as "A-1120." Adhesion promoters are disclosed also in U.S.Pat. No. 3,881,043.

The sheet of the present invention possesses exceptional adhesiveproperties of the type required in a safety windshield in the absence ofthe use of an adhesion promoter. However, it should be understood thatan adhesion promoter may be used in the practice of the presentinvention for reasons which are independent of the inherent adhesiveproperties possessed by the sheet invention. For example, an adhesionpromoter can be used to compensate for a decrease in sheet adhesion dueto the presence of an adhesion inhibitor such as a silicone flowenhancing agent, or to improve the adhesive properties of the sheet in amanner such that they exceed the present industry safety standards forthe adhesive requirements of a glazing laminate.

An embodiment of the present sheet of particular interest comprises asingle ply of flexible, transparent, adhesive and energy-absorbingpolyurethane. In this embodiment, the single polyurethane ply exhibitsalso useful surface characteristics including scratch and abrasionresistance.

The surface of the present sheet is substantially non-tacky at roomtemperature (for example, about 15° C. to about 35° C.), that is, attemperatures likely to be encountered in a facility in which the sheetis manufactured, stored, and/or used in preparing a glazing laminate. Attemperatures in excess of about 35° C., its adhesive surface is softenedto the extent that when the sheet is pressed to a glass or plasticsubstrate, it is capable of flowing and adhering to the substrate to anextent that the sheet does not slip or slide on the surface of thesubstrate. Treatment of the assembly resulting from the sheet andsubstrate at elevated temperature and pressure forms a laminatecomprising an exposed ply of the present sheet. The adhesive bond formedby the sheet to the underlying ply of the laminate maintains its bond,even in the absence of the use of an adhesion promoter, under adversetemperature and humidity conditions, as evaluated in ANSI Z26 Test Nos.3 and 4, described in detail below.

The exceptional nature of the adhesive bond of the sheet, as well as theenergy-absorbing, optical and other properties of the sheet andlaminates according to the present invention may be evaluated accordingto standard tests published by the American Standards Association inAmerican Standard Safety Code for Safety Glazing Materials for GlazingMotor Vehicles Operating on Land Highways, Revision Z26.1-1966("ANSI-Z26") and according to tests published in Addendum 42: RegulationNo. 43 of the "United Nations Agreement Concerning the Adoption ofUniform Conditions of Approval and Reciprocal Recognition of Approvalfor Motor Vehicle Equipment and Parts" (hereinafter "ECE R43"), herebyincorporated by reference. The temperature and moisture resistance ofthe present laminates may be evaluated by the ANSI-Z26 Humidity and Boiltest procedures, reproduced below.

Humidity, Test No. 3

5.3.1 Purpose of Test

The purpose of this test is to determine whether the safety glass willsuccessfully withstand the effect of moisture in the atmosphere over anextended period of time.

5.3.2 Procedure

Three 12×12-inch flat specimens, as submitted, shall be kept for 2 weeksin a closed container over water. The temperature of the air in thecontainer shall be maintained within the limits of 120° and 130° F.(These conditions give a relative humidity of about 100 percent.)

5.3.3. Interpretation of Results

No separation of materials shall develop, except for occasional smallspots, no one of which shall extend inward from the adjacent edge of thespecimen to a depth of more than 1/4 inch.

Boil, Test No. 4 (this test is not applicable to multiple glazed units.)

5.4.1 Purpose of Test

The purpose of this test is to determine whether the safety glass willsuccessfully withstand exposure to tropical temperatures over anextended period of time.

5.4.2 Procedure

Three 12×12-inch flat specimens, as submitted, shall be immersed,vertically on edge, in water at 150° F. for 3 minutes and then quicklytransferred to and similarly immersed in boiling water. The specimensshall be kept in the boiling water for 2 hours and then removed.

5.4.3. Interpretation of Results

The glass itself may crack in this test, but no bubbles or other defectsshall develop more than 1/2 inch from the outer edge of the specimen orfrom any cracks that may develop. Any specimen in which the glass cracksto an extent confusing the results shall be discarded without prejudiceand another specimen shall be tested in its stead.

The laminates of the present invention both prepared with and without anadhesion promoter additive, pass ANSI-Z26 Test Nos. 3 and 4.

A polyurethane sheet within the scope of the present invention can beprepared from a reaction mixture comprising a polyisocyanate component,a polymeric polyol and a low molecular weight diol. A preferredembodiment of the present invention comprises a polyurethane formed froma reaction mixture including a polyisocyanate monomer componentcontaining about 2 to about 10 wt. % of urea groups.

The polyurethane-forming components are present in the reaction mixturesuch that the molar ratio of the available NCO groups to available OHgroups is about 0.8:1 to about 1:1. As the NCO/OH ratio becomes greaterthan one, for example, about 1.01:1 to about 1.1:1, the sheet becomesmore rigid. When the polyurethane-forming monomers are all difunctional,the NCO/OH ratio is preferably about 0.9:1 to about 1:1, and mostpreferably the ratio is about 1:1.

The polyisocyanate component comprises an aliphatic, cycloaliphatic orprepolymer polyisocyanate and preferably a diisocyanate. Exemplarydiisocyanates include: 1,6-hexamethylene diisocyanate (HMDI);2,2,4-trimethyl-1,6-hexane diisocyanate (TMDI);bis(4-isocyanatocyclohexyl)methane in any number of differing isomericratios, preferably the isomeric mixture sold as "Hylene W";bis(3-methyl-4-isocyanatocyclohexyl)methane;2,2-bis(4-isocyanatocyclohexyl) propane;3-isocyanatomethyl-3,5,5-trimethylcyclohexylisocyanate, referred to alsoas isophorone diisocyanate or IPDI; transcyclohexane-1,4-diisocyanate;m-xylylene diisocyanate; m- and p-tetramethylxylylenediisocyanate; and1,3-(diisocyanatomethyl) cyclohexane.

As mentioned above, a preferred polyisocyanate component includes about2 to about 10 wt. % of urea groups, more preferably about 5 to about 7wt. % of urea groups. A particularly preferred polyisocyanate componentcomprises a cycloaliphatic diisocyanate including about 5 to about 7 wt.% of urea groups and is most preferably a urea-modified isophoronediisocyanate comprising a mixture of isophorone diisocyanate and theurea-containing diisocyanate adduct of isophorone diisocyanate andwater, such as N,N'-bis(isophorone isocyanato)urea, and in which the NCOcontent of the mixture is about 30 to about 33 wt. %. A most preferredurea-containing polyisocyanate monomer component comprises a mixture ofisophorone diisocyanate, "IPDI", and the urea-containing IPDI product,"IPDI H-2921", each product sold by Huls Co.

The polymeric polyol component comprises a polyether diol or polyesterdiol having a MW of about 500 to about 4000. Exemplary polyester diolsinclude: polylactone diols, for example, polycaprolactone diol; and, theesterification products of a diacid and a low molecular weight diol.Exemplary diacids are adipic, succinic, palmitic, azelaic, sebacic andphthalic acid. Exemplary low molecular weight diols are ethylene glycol,propane-1,3-diol, butane-1,4-diol, and hexane-1,6-diol. Exemplarypolyether diols include those described by the linear chain formulaH-[O(CH₂)_(n) ]_(m) OH, where n is about 2 to about 6, and the branchedchain formula ##STR1## where, in both formulae, m is such that the MW ofthe polymer is about 500 to about 4000. A portion of the polyolcomponent may be replaced with a polyamine monomer.

The preferred polymeric diol comprises a polyether diol, and mostpreferably polytetramethylene glycol having a molecular weight of about1000.

Exemplary short chain diols for use as chain extenders have a MW of lessthan about 300 and preferably a MW less than about 150 and include:ethylene glycol; propane-1,2-diol; propane-1,3-diol; butane-1,2, -1,3,or -1,4-diol; dimethyl-2,2-propane-1,3-diol (neopentylglycol);pentane-1,5-diol; hexane-1,6-diol; octane-1,8-diol; decane-1,10-diol;dodecane-1,12-diol; cyclohexanedimethanol; bisphenol A;2-methylpentane-2,4-diol; 3-methylpentane-2,4-diol;2-ethylhexane-1,3-diol; 2,2,4-trimethylpentane-1,3-diol;diethyleneglycol; triethyleneglycol; tetraethyleneglycol;2-butyne-1,4-diol; butene-1,4-diol; decynediol; substituted and/oretherified, hydroquinone-bis-hydroxyethylether; bisphenol A, etherifiedby two or four groups of propylene oxide; or dimethylolproponic acid.The most preferred short chain diol for use as a chain extender isbutane-1,4-diol.

The molar ratio of polymeric diol to chain extender diol may beexpressed in terms of an OH equivalent ratio and varies as a function ofthe properties desired in the polyurethane sheet. A preferred molarratio of polymeric diol to chain extender diol is about 0.3:1 to about1:1. As the percentage of chain extender diol is increased, theresulting polyurethane sheet may harden and its modulus of elasticityincrease.

A particularly preferred embodiment of the present invention comprises apolyurethane sheet formed from a monomer mixture including a smallamount of tri- or higher functional monomers, such as a polyisocyanatecomponent including less than about 15 NCO equivalent percent of atriisocyanate such as a biuret or a triisocyanurate; or a polyolcomponent including a small amount of a polyol having a hydroxyfunctionality greater than two and, particularly, a polyol componentsuch as an aliphatic polyol, for example, glycerol, trimethylolpropane,or a polyether or a polylactone polyol, having a functionality greaterthan two, such as a triol, and having a MW of about 90 to about 1000. Anexemplary polyol comprises a polypropylene glycol ester of a mixture ofdimerized and trimerized linolenic acid, having an OH functionalitybetween 2 and 3. A most preferred aliphatic polyol is a polymeric triolwhich most preferably comprises polycaprolactone triol. A polyurethanesheet prepared from a composition including a monomer other than a diolor diisocyanate exhibits improved cohesive properties.

The OH-equivalent ratio of the polyol of functionality greater than two(hereinafter referred to as the "triol") relative to the polymeric dioland chain extender diol can vary. The polymeric diol comprises about 30to about 45 OH equivalent percent of the total OH content in thepolyurethane-forming reaction mixture; the chain extender diol comprisesabout 20 to about 70 OH equivalent percent; and, the triol comprises upto about 35 OH equivalent percent, such as between about 0.05 and about35 OH equivalent percent. A preferred molar ratio of polymeric diol totriol is about 1.5:1 to about 4:1, and that of polymeric diol to chainextender diol is about 0.5:1 to about 0.8:1.

A particularly preferred embodiment of the present invention comprises apolyurethane sheet formed by "reactive casting", a term used herein torefer to a process in which a liquid film comprising a monomericreaction mixture is formed on a horizontal support and a solid fullycured polymeric sheet prepared by polymerizing the reaction mixture inthe form of the liquid film at a temperature (for example, between about80 to about 140° C., and preferably about 100 to about 140° C.) andwithin a time period practical for use in a continuous industrialprocess. In this connection, a preferred embodiment of the presentinvention comprises a preformed sheet prepared by:

(1) forming on a horizontal support a liquid film comprising asolvent-free mixture of monomers capable of forming a polyurethane and apolyurethane forming catalyst;

(2) maintaining said liquid film at a temperature and for a timesufficient to permit the formation of a uniformly thick and level film;and

(3) raising the temperature of said uniformly thick and level liquidfilm and maintaining the film at an elevated temperature sufficient tofully polymerize the film into a solid polyurethane within less thanabout one hour while it is positioned on said horizontal support.

A particularly preferred means for preparing the present sheet comprisesraising the temperature of the uniformly thick and level film to saidelevated temperature within a minimal time period such as less thanabout 3 minutes, and polymerizing the liquid film in less than about 30minutes.

The term "uniformly thick and level liquid film" describes a film whichhas a uniform thickness on a level support such that a solid filmprepared therefrom has optical properties acceptable for glazingapplications.

An embodiment of the present invention of particular interest relates toa two-ply sheet, one surface of which comprises a self-healing thermosetpolymeric material, the other surface of which comprises the presentreactive cast polyurethane.

A particularly preferred polyurethane for use in making a sheetaccording to the present invention by reactive casting, as describedabove, is formed from:

(A) a cycloaliphatic polyisocyanate component including about 5 to about7 wt. % urea groups and about 30 to about 33 wt. % of NCO groups;

(B) a polyol component including:

(1) about 30 to about 45 OH equivalent percent of a polymeric diolhaving a MW of about 500 to about 3000;

(2) about 20 to about 70 OH equivalent percent of a chain extender diol;and

(3) about 0.05 to about 35 OH equivalent percent of a triol; and

(C) a polyurethane-forming catalyst;

wherein the NCO/OH ratio of said mixture is about 0.8:1 to about 1:1.

Exemplary polyurethane forming catalysts are: a tin catalyst, forexample, dibutyltin dilaurate, tributyltin oxide, tin octoate; anorganomercuric catalyst, for example, mercuric phenyl ester; and anamino catalyst, for example, diazabicyclo-(2,2,2)-octane, and1,8-diazabicyclo(5,4,0)-1-decene-7. A tin catalyst is preferred in anamount comprising greater than about 0.01 to about 0.05 weight percentbased on the total weight of the liquid film composition.

The composition forming the present sheet can also include a stabilizersuch as bis(2,2,6,6-tetramethyl-4-piperidyl) sebecate or a phenolicantioxidant, and a sheeting or flow enhancing agent such as afluoroalkylated ester, an acrylic resin, or a silicone resin. Afluoroalkylated ester sheeting agent is preferred.

In a most preferred form, the above composition has a viscosity suchthat the liquid film formed therefrom attains a uniformly thick andlevel form on the horizontal support within about 0.5 to about 5minutes.

A preferred horizontal support has a surface which is smooth, level anddefect-free and renders the film formed thereon with a correspondingoptically defect-free surface. A most preferred horizontal supportcomprises a release surface such as a supported Teflon material or thelike or a support coated with a release agent such as a modifiedaddition product of ethylene oxide of the formula

    R.sub.1 --X--(C.sub.2 H.sub.4 O).sub.n --R.sub.2

in which:

R₁ represents an alkyl group containing about 8 to about 18 carbon atomsor an alkyl-aryl group containing about 6 to about 12 carbon atoms inthe alkyl chain;

R₂ represents one of the following groups:

PO₃ M₂

CO--CH(SO₃ M)--CH₂ COOM

CO--C₆ H₄ --COOM

M is an alkali metal and

X represents one of the following groupings:

O, CO--O or CO--NH and

n is about 1 to about 100.

The most preferred release agent in the practice of the presentinvention is a disodium polyether sulfosuccinate as disclosed in U.S.Pat. No. 4,331,736.

The polyurethane sheet may be removed from the horizontal support andstored for later use or used immediately to form a glazing laminate asdescribed herein below. A particular aspect of the present methodrelates to a sheet wherein the adhesive surface opposite that surfaceformed in contact with the horizontal support exhibits preferredadhesive properties. Another aspect of the present method relates to theimproved surface characteristics, such as the scratch and abrasionresistant properties, exhibited by the surface formed in contact withthe horizontal release support.

The reactive cast polyurethane sheet possesses both thermoplastic- andthermoset-type properties. For example, it has thermoset-type propertiesin that it is infusible and insoluble in most polyurethane solvents suchas tetrahydrofuran and dimethylformamide and it exhibitsthermoplastic-type properties in that it softens and adheres at elevatedtemperatures. Furthermore, the reactive cast sheet exhibits surprisingenergy absorbing properties. Although applicants do not wish to be boundby any particular theory, it is believed that the temperature, catalystconcentration, NCO/OH ratio and other parameters of reactive castingpromote the formation of secondary chemical branching such as theformation of allophanate and/or biuret linkages, and that this secondarybranching is, in part, responsible for the properties of the presentsheet. Furthermore, it should be noted that when the NCO/OH ratio isless than about 1:1 and the polyurethane-forming monomer components aredifunctional in nature, the secondary branching described above does notoccur to any significant extent and the energy-absorbing properties arereduced.

In a most preferred embodiment of the present invention, the presentreactive cast sheet exhibits the following mechanical properties,measured according to AFNOR/NFT standard 46 002, 51 034 and 54 108:

a tensile strength at 10 percent elongation, σy at -20° C. less than orequal to about 300 daN/cm² ;

a tensile strength at break, σR at +40° C. greater than or equal toabout 200 daN/cm² ;

an elongation to rupture εR at +20° C. ranging from about 250 to about500 percent; and

an initial tear strength Ra at +20° C. with a thickness greater than orequal to about 90 daN/cm.

One embodiment of the present sheet comprises a single ply whichexhibits, in addition to energy-absorbing properties, abrasion- andscratch-resistant properties which render it effective for use as anexposed ply in a bilayer laminate. In this embodiment, the scratchresistance of the sheet is greater than 20 grams, and, the abrasionresistance is less than 4 percent, both properties being measuredaccording to the tests described in detail below.

As mentioned above, another embodiment of the present sheet comprises atwo-ply sheet, one ply of which comprises a self-healing, thermosetpolymeric material and the other ply of which comprises the energyabsorbing, adhesive polyurethane described hereinabove. A preferredmethod for making such a two-ply sheet involves a continuous operationin which a sheet of the thermoset polymeric material is first formed byreactive casting after which the aforementioned adhesive polyurethane isformed by reactive casting on the thermoset sheet. More particularly,this method comprises:

(1) forming on a horizontal support a liquid film comprising a mixtureof monomers capable of forming a thermoset polymeric material;

(2) polymerizing said liquid film thereby forming a solid underlyingsupported ply;

(3) forming on said supported ply an overlying liquid film comprising asolvent-free mixture of monomers capable of forming a polyurethane and apolyurethane-forming catalyst;

(4) maintaining the temperature of said overlying film for a timesufficient to permit the formation of a uniformly thick and level liquidfilm;

(5) raising the temperature of said level liquid film and maintaining anelevated temperature sufficient to fully polymerize said film and forman overlying solid polyurethane film in less than about an hour, therebyresulting in a supported multi-ply sheet; and

(6) removing said multi-ply sheet from said support.

A preferred self-healing material exhibits properties such that, undernormal temperature conditions, the aforementioned self-healing ply has ahigh capacity for elastic deformation, a low modulus of elasticity, lessthan 2000 daN/cm² and preferably less than 200 daN/cm², and anelongation at breaking of more than 60 percent with less than 2 percentplastic deformation and preferably an elongation at breaking of morethan 100 percent with less than 1 percent plastic deformation. Thepreferred films of this type are thermoset polyurethanes with a modulusof elasticity of about 25 to 200 daN/cm² and an elongation of about 100to 200 percent with less than 1 percent plastic deformation.

Examples of polyisocyanates suitable for the preparation of thesethermoset polyurethanes include: 1,6-hexane-diisocyanate;2,2,4-trimethyl-1,6-hexanediisocyanate;2,4,4-trimethyl-1,6-hexanediisocyanate;1,3-bis(isocyanatomethyl)benzene; bis(4-isocyanatocyclohexyl)-methane;bis(3-methyl-4-isocyanatocyclohexyl)methane;2,2-bis(4-isocyanatocyclohexyl)propane; and3-isocyanatomethyl-3,5,5-tri-methyl-cyclohexylisocyanate; and thebiurets, isocyanurates and NCO prepolymers thereof. Examples of polyolssuitable for the preparation of the thermoset polyurethanes includestraight-chained and branched polyols, such as the following: thepolyesterpolyols and the polyetherpolyols obtained by reaction ofpolyfunctional alcohols such as 1,2,3-propanetriol(glycerol);2,2-bis(hydroxymethyl)-1-propanol(trimethylolethane);2,2-bis(hydroxymethyl)-1-butanol(trimethylolpropane);1,2,4-butane-triol; 1,2,6-hexane-triol;2,2-bis(hydroxymethyl)-1,3-propane-diol(pentaerythritol); and1,2,3,4,5-5-hexane-hexol(sorbitol); with either the aliphatic diacidssuch as malonic acid; succinic acid; glutaric acid; adipic acid; subericacid; and sebacic acid; or with the cyclic ethers, such as ethyleneoxide; 1,2-propylene oxide and tetrahydrofuran.

The molecular weight of the polyols is about 250 to about 4000 andpreferably is about 450 to about 2000. Mixtures of differentpolyisocyanate and polyol monomers can be used. An especially preferredthermoset polyurethane is the one disclosed in U.S. Pat. Nos. 3,979,548and 4,232,080.

The thickness of the mono-ply sheet can be varied depending on the useof the sheet. It is believed that a great many applications of use willbe served satisfactorily by a sheet thickness of about 0.1 to about 1.0mm, and particularly a thickness of about 0.3 to about 0.8 mm. Inglazing laminate applications where impact resistance and energyabsorbing properties of the sheet are desired, the thickness of thesheet is preferably greater than about 0.4 mm and most preferablygreater than about 0.5 mm. Exemplary thicknesses of the two-ply sheetare about 0.1 to about 1.0 mm, preferably greater than about 0.5 mm. Insuch two-ply sheets, the energy-absorbing ply is about 0.1 to about 0.8mm thick, and preferably greater than about 0.4 mm thick.

The present sheet may be utilized in a variety of laminate applications,including lenses, windows or transparencies for use in the optical,building, transportation and security industries, such asbullet-resistant windows or partitions, and side or lateral windows inmotor vehicles, planes and trains. Additionally, the present sheet maybe laminated to a container, for example, glass or plastic bottles. Thepresent invention particularly relates to a bilayer glazing laminatecomprising a single sheet of glass or a rigid plastic substrate and thepresent preformed sheet. A glazing laminate of particular interest is avehicle windshield comprising an outer-glass ply and an inner ply ofpoly- urethane.

The glass ply which can be employed in the laminates of the presentinvention can be of any type, depending upon the intended use of thelaminate, but preferably is a clear, low-colored, transparent type ofglass, such as the well-known silica glass, particularlysoda-lime-silica glass. The nature and composition of various sodaglasses is known in the art and is described, for example, in theEncyclopedia of Chemical Technology, by Kirk-Othmer, published byInterscience Encyclopedia Inc., New York, New York, Vol. 7, pages181-189. The glass can be strengthened by either thermal or chemicaltempering.

The thickness of the glass can vary depending on the ultimate end use.Typically, the glass can have a thickness of from 50 to 500 mils (0.127to 1.27 cm). For automobile and other motor vehicle window uses, theglass will preferably have a thickness between about 65 and 180 mils(0.165 and 0.457 cm), and most preferably about 3.0 mm.

Besides glass, other rigid transparent sheets, such as polycarbonate andacrylic sheeting, can be used to form the laminates of the presentinvention. Also, besides bilayer laminates, the polyurethane interlayersof the present invention can be used to make tri- and multi-plylaminates in which the sheet of the present invention may be interposedbetween alternating rigid transparent sheets (e.g., glass, polycarbonateor acrylic). Also, the polyurethane sheet of the present invention canbe used in combination as a flexible ply between alternating layers ofrigid transparent sheet in combination with other flexible plastic pliessuch as polyvinyl butyral. Such multi-ply laminates are useful asaircraft transparencies or as bullet-proof glass for armored vehicles.

In preparing a glazing laminate, the present preformed sheet can beassembled by using pressure and/or heat and is preferably contacted witha rigid plastic or glass ply under pressure, for example, by pinchingbetween the rollers of a calenderer. The adhesive bond may be improvedby subjecting the aforesaid assembly to an autoclaving cycle, forexample, for about one to about two hours at a temperature of about 100°C. to about 140° C. and a pressure of about 3 to about 15 bars. A bakingcycle may be used in place of an autoclaving cycle.

Another aspect of the present invention relates to a method forpreparing a glazing laminate comprising:

(1) providing a preformed polyurethane sheet formed on a horizontalsupport, according to the method described above.

(2) removing said solid polyurethane sheet from said horizontal support;

(3) contacting a glass or plastic ply surface with the surface of saidsheet opposite that formed in contact with said horizontal support,thereby forming an assembly; and

(4) treating said assembly at elevated temperature and pressure.

In the two ply sheet embodiment of the present invention, the surfaceapplied to the glass or plastic ply is that of the energy-absorbingpolyurethane ply.

The adhesive strength of the laminates of the present invention may bemeasured by the 90 degree angle peel test described in NASA Tech Brief65-10173. A 5 cm wide strip of laminate is adhered to a pull bar and aseparating force applied to the laminate at a 90° angle and adjusted toresult in separation of the laminate at a rate of 5 cm/min. The adhesiveforce needed to separate the laminate is reported hereinbelow in unitsof decanewtons (daN) per 5 linear cm.

The degree of adhesion in bilayer glass laminates of the presentinvention is recommended to be about 2 daN/5 cm to about 15 daN/5 cm,preferably about 3 daN/5 cm to about 11 daN/5 cm. This adhesion is lowenough to allow sufficient polyurethane ply to release from the glassply so that it can stretch without tearing to absorb impacting energy,yet the degree of adhesion is sufficient for retention of broken glass.Higher degrees of adhesion, that is, much higher than about 15 daN/5 cmcan result in decreases in impact resistance, described in more detailbelow. Lower degrees of adhesion, that is, lower than about 2 daN/5 cmare insufficient for commercial vehicle use in that delamination mayoccur, particularly under high humidity conditions.

Furthermore, the degree of adhesion in the present laminate should berelatively stable over a wide range of temperature and humidityconditions. By relatively stable under a wide range of temperature andhumidity conditions is meant that although there may be fluctuations inthe adhesive value over a period of time, the degree of adhesion remainswithin the range described above.

A particularly preferred embodiment of the present invention relates toa bilayer glazing laminate which exhibits energy-absorbing, optical,moisture resistant, and abrasion resistant properties in compliance withU.S. and European automotive safety regulations, and, in particular,ANSI-Z26 and ECE R43 standards. In addition to the properties measurableby the aforesaid standards, glazing laminates prepared from the presentmono-ply and multi-ply sheet exhibit scratch resistant and plasticrecovery after deformation properties, including self-healingproperties. These properties may be evaluated by the Erichsen Testdescribed below.

Scratch resistance--Scratch resistance may be measured by the ErichsenType 413 tester equipped with a diamond stylus having a tip radius of 15microns and an included angle of 50°. A sample of the sheet to be testedis adhered to a substrate such as glass, which is rotated duringtesting. The diamond stylus is placed on top of the surface to be testedand is attached to a calibrated arm which permits a weight of from 0 to100 grams to be exerted through the stylus. The laminated sheet isrotated during testing and the highest value (in grams) determined atwhich the sheet is not permanently deformed by tearing.

Sheets of the present invention exhibit the property of recovery afterdeformation, meaning that a deformation in the surface of the presentsheet will disappear or recover within a period of time of less than afew seconds to several hours, for example, less than about 20 hours.Materials which have both a high scratch resistance that is greater thanabout 20 g as measured by the Erichsen test and a short recovery timemay be described as "self-healing."

The following test procedures are used to determine the abrasionresistance, and impact resistance of bilayer laminates of the presentinvention.

Abrasion resistance--Abrasion resistance may be determined according toANSI-Z26 Test No. 17, as applicable to bilayer glass-plastic laminatesin according with 49 CFR §571.205, S.5.1.2.3 (as amended Nov. 16, 1983)(corresponding to Test No. 4, ECE R43), portions of which are reproducedbelow.

5.17 Abrasion Resistance (Plastics), Test No. 17

5.17.1 Purpose of Test

The purpose of this test is to determine whether the plastic has acertian minimum resistance to abrasion.

5.17.2 Procedure

5.17.2.1 Apparatus

(1) The apparatus for the abrasion shall be the Taber Abraser or itsequivalent. A load of 500 grams shall be employed on each wheel.

. .

(3) An abrasive wheel meeting the following requirements at the time ofthe test shall be used:

. .

(b) . . . The test shall be made with the pressure applied verticallyalong a diameter of the wheel, and reading taken 10 seconds after fullapplication of the pressure. Each wheel shall have a durometer hardnessof 72±5.

(4) The turntable of the Abraser shall rotate substantially in a planewith a deviation at the distance of 1/16 inch (1.59 mm) from itsperiphery of not greater than ±0.002 inch (±0.05 mm).

(5) An integrating sphere, photoelectric photometer constructedessentially as shown in FIG. 5 or 6 and conforming to the requirementsshown below shall be used to measure the light scattered by the abradedtrack . . . .

5.17.2.2 Test Specimens

(1) Three 4×4-inch (102×102-mm), flat specimens, as submitted, havingboth surfaces substantially plane and parallel, shall be tested.

. .

5.17.2.3 Conditioning of Specimens

The specimens shall be conditioned prior to testing for a minimum timeof 48 hours at 71° F. to 75° F. (22° C. to 24° C.) and 50% ±2% relativehumidity.

5.17.2.4 Method of Test

The test method shall be as follows:

(1) Level the Taber Abraser.

(2) . . . The load to be used is 500 grams on each wheel.

. .

(4) Measure the initial haze of the specimen at a minimum of fourequally spaced points in the unabraded area in accordance with5.17.2.1(5)(m). The results shall be averaged for each specimen. In lieuof the four measurements, an average value may be obtained by rotatingthe specimen at three or more revolutions per second.

(5) The specimen shall be mounted on the specimen holder so that itrotates substantially in a plane and subjected to abrasion for 100cycles. Specimens shall be carefully wiped after abrasion with dry lenspaper (or its equivalent).

(6) Measure the light scattered by the abraded track at a minimum offour equally spaced points along the track. . .

The average initial haze determined by 5.17.2.4(4) shall be subtractedfrom the average total light scattered as measured by 5.17.2.4(6), thedifference representing the light scatter resulting from abrading thespecimen.

5.17.3 Interpretation of Results

The arithmetic mean of the percentages of light scattered by the threespecimens as a result of abrasion shall not exceed 15.0%.*

The energy-absorbing properties of the present laminates can beevaluated according to Regulation R43, Test Nos. 4.2 (large ball test[2.26 kg]), and 4.3 (small ball test [227 g]), portions of which arereproduced below.

4.2. Ball-impact test--2.26 kg

4.2.1. Number of test pieces

Six square test pieces of 300±¹⁰ ₀ mm side shall be subjected totesting.

4.2.2 Test method

4.2.2.1. The method shall be that described in annex 3, paragraph 2.2.[impact occurs on the plastic face of the bilayer]*

4.2.2.2. The height of drop (from the underface of the ball to the upperface of the test piece) shall be 4 m±²⁵ ₀ mm.

4.2.3. Interpretation of results

4.2.3.1. The ball-impact test shall be deemed to have given asatisfactory result if the ball does not pass through the glazing withinfive seconds after the moment of impact.

4.2.3.2. A set of test pieces submitted for approval shall be consideredsatisfactory from the point of view of mechanical strength if one of thefollowing two conditions is met; that is to say, if:

4.2.3.2.1. All the tests give a satisfactory result; or

4.2.3.2.2. One test having given an unsatisfactory result, a furtherseries of tests carried out on a new set of test pieces givessatisfactory results.

4.3. Ball-impact test--227 g.

4.3.2. Number of test pieces.

Twenty square test pieces of 300±¹⁰ ₀ mm side shall be subjected totesting.

4.3.3. Test method

4.3.3.1. The method used shall be that described in annex 3, paragraph2.1. [impact on glass side of bilayer laminate]*

Ten specimens shall be tested at a temperature of +40° C. ±2° C. andthen at a temperature of -20° C.±2° C.

4.3.3.2. The height of drop for the various thickness categories and themass of the detached fragments are given in the table below:

    ______________________________________           +40° C.                         -20° C.                      Maximum-          Maximum    Thickness of      permitted         permitted    Test Piece             Height of                      mass of the                                 Height of                                        mass of the    mm       fall (m) fragments (g)                                 fall (m)                                        fragments (g)    ______________________________________    e < 4.5  9        12         8.5    12    ______________________________________

. .

4.3.4. Interpretation of results

4.3.4.1. The ball-impact test shall be deemed to have given asatisfactory result if the ball does not pass through the glazing. Ifthe interlayer is not torn, the weight of fragments detached from theside of the glass opposite to the point of impact must not exceed theappropriate values specified in paragraph 4.3.3.2. above.

4.3.4.2. A set of test pieces submitted for approval shall be consideredsatisfactory from the point of view of mechanical strength if one of thefollowing two conditions is met; that is to say, if:

4.3.4.2.1. Not less than eight tests at each test temperature gives asatisfactory result; or

4.3.4.2.2. More than two tests at each test temperature having given anunsatisfactory result, a further series of tests carried out on a newset of test pieces gives satisfactory results.

Impact resistance may be evaluated also according to ANSI-Z26 Test No.26 (Large Ball Test), Test No. 12 (Small Ball Test) and Test No. 9(0.702 Dart Test), hereby incorporated by reference. Bilayer laminatesof the present invention wherein the present preformed sheet comprisesan adhesive ply of greater than about 0.4 mm thick, and preferablygreater than about 0.5 mm thick, exhibit impact resistant propertieswhich comply with the ECE R43 and ANSI-Z26 standards described above.

Examples of the compositions, preformed sheets, glazing laminates andmethods for the preparation thereof according to the present inventionare described below.

EXAMPLE 1

A composition is prepared by mixing at about 30° to 40° C. Components A,B, and C listed below.

    ______________________________________                        Equivalents                        NCO   OH     Wt %    ______________________________________    Component A:    urea modified monomer mixture of                          1       --     --    3-isocyanato-3,5,5-trimethylcyclo-    hexane isocyanate    [NCO content is about 31.5% by weight]    Component B:    polytetramethyleneglycol, MW 1000*                          --      0.37   --    1,4-butanediol        --      0.63   --    Component C:    dibutyl tin dilaurate --      --     0.02    sheeting agent        --      --     0.05    stabilizer            --      --     0.50    ______________________________________     *sold as Polymeg 1000 by the Quaker Oats Co.

The composition is degassed in vacuo, heated to a temperature of about40° C. and cast onto a movable horizontal release-coated glass supportmaintained at a temperature of about 40° C. The composition is castusing a casting head such as disclosed in French Pat. No. 2,347,170. Thecomposition is allowed to form a uniformly thick and level liquid filmabout 0.76 mm thick on the horizontal support, after which thetemperature of the level liquid film is raised within a period of timeof less than about 5 minutes to about 120° C. and maintained at about120° C. for about 25 minutes. The resulting fully polymerizedpolyurethane sheet is removed from the horizontal support and may bestored for later use or used immediately in the manufacture of a glazinglaminate, described in more detail below.

The sheet prepared above is assembled with a glass sheet (2.6 mm thick)by contacting the surface of the glass with the surface of the sheetopposite that formed in contact with the aforesaid horizontal support.The resulting assembly is subjected to a prepressing stage by passing itbetween two calenderer rollers, for example, by using the apparatusdisclosed in U.S. Pat. No. 4,327,634. The prepressed laminate issubjected to an autoclaving cycle comprising treating the laminate at atemperature of about 135° C. and a pressure of about 10 bars for abouttwo hours. The properties of the resulting laminate are presented inTable I below.

EXAMPLE 2

A 0.66 mm thick sheet is formed using the composition comprisingComponents A, B, and C, described below, in accordance with the methoddescribed in Example 1.

    ______________________________________                        Equivalents                        NCO   OH     Wt %    ______________________________________    Component A:    urea modified monomer mixture of                          1       --     --    3-isocyanato-3,5,5-trimethylcyclohexane    isocyanate    [NCO content is about 31.5% by weight]    Component B:    polytetramethyleneglycol, MW 1000*                          --      0.35   --    1,4-butanediol        --      0.55   --    polycaprolactone triol**                          --      0.10   --    Component C:    dibutyl tin dilaurate --      --     0.02    sheeting agent        --      --     0.05    stabilizer            --      --     0.50    ______________________________________     *sold as Polymeg 1000 by the Quaker Oats Co.     **sold as NIAX 301 by Union Carbide.

A glazing laminate comprising the sheet of Example 2 is prepared inaccordance with the method described in Example 1 and the propertiesthereof are described in Table I below.

EXAMPLE 3

A 0.70 mm thick sheet is formed in accordance with the method asdescribed in Example 1, from the composition comprising Components A, Band C, described below.

    ______________________________________                        Equivalents                        NCO   OH     Wt %    ______________________________________    Component A:    urea modified monomer mixture of                          1       --     --    3-isocyanato-3,5,5-trimethyl-    cyclohexane isocyanate    [NCO content is about 31.5% by weight]    Component B:    polytetramethyleneglycol, MW 1000*                          --      0.35   --    1,4-butanediol        --      0.45   --    polycaprolactone triol**                          --      0.20   --    Component C:    dibutyl tin dilaurate --      --     0.02    sheeting agent        --      --     0.05    stabilizer            --      --     0.50    ______________________________________     *sold as Polymeg 1000 by the Quaker Oats Co.     **sold as NIAX 301 by Union Carbide.

A glazing laminate including the sheet of Example 3 is prepared inaccordance with the method described in Example 1 and the propertiesthereof are described in Table I below.

EXAMPLE 4

A multi-ply sheet including a layer of self-healing thermoset materialis prepared by casting, on a horizontal release-coated glass support, aliquid mixture comprising:

1000 g of a polyether prepared by the condensation of 1,2-propyleneoxide with 2,2-bis(hydroxymethyl)-1-butanol and having a free hydroxylcontent of about 10.5 to about 12 percent and a molecular weight ofabout 450;

10 g of a stabilizer;

0.5 g of dibutyl tin dilaurate;

1 g of a sheeting agent; and

1020 g of a biuret of 1,6-hexanediisocyanate having a free NCO contentof about 23.2 percent.

The cast liquid film forms a uniformly level layer 0.19 mm thick and isfully cured to a solid supported thermoset polyurethane by raising thetemperature of the film to about 120° C. for about 15 minutes. The curedthermoset polyurethane has self-healing properties.

An energy-absorbing adhesive ply of polyurethane is formed on the solidsupported thermoset material by casting a 0.53 mm thick liquid filmcomprising a mixture of Components A, B, and C, described below.

    ______________________________________                        Equivalents                        NCO   OH     Wt %    ______________________________________    Component A:    urea modified monomer mixture of                          1       --     --    3-isocyanato-3,5,5-trimethylcyclo-    hexane isocyanate    [NCO content is about 31.5% by weight]    Component B:    polytetramethyleneglycol, MW 1000*                          --      0.37   --    1,4-butanediol        --      0.63   --    Component C:    dibutyl tin dilaurate --      --     0.02    sheeting agent        --      --     0.05    stabilizer            --      --     0.50    ______________________________________     *sold as Polymeg 1000 by the Quaker Oats Co.

The solid supported overlying ply of polyurethane is formed according tothe method described in Example 1 above. The resulting supported two-plysheet is removed from the horizontal support and stored for later use orused immediately in the manufacture of a glazing laminate. A glazinglaminate prepared from the two-ply sheet of the present example isassembled by contacting a glass sheet (2.6 mm thick) with the surface ofthe two-ply sheet opposite that of the thermoset self-healing surface.The resulting assembly is laminated as described above, and theproperties thereof presented in Table I below.

EXAMPLE 5

A multi-ply sheet having a 0.41 mm thick self-healing thermoset ply and0.29 mm thick energy-absorbing adhesive polyurethane ply is preparedaccording to the method and compositions described in Example 4 above.

A glazing laminate is manufactured from this sheet and the propertiesthereof presented in Table I below.

EXAMPLE 6

A multi-ply sheet having a 0.315 mm thick self-healing thermoset ply anda 0.415 mm thick energy-absorbing polyurethane ply is prepared accordingto the method and compositions described in Example 4 above.

A glazing laminate is manufactured from this sheet and the propertiesthereof presented in Table I below.

EXAMPLE 7

A multi-ply sheet having a 0.39 mm thick self-healing thermoset ply anda 0.39 mm energy-absorbing polyurethane ply is prepared according to themethod described in Example 4 above, except that the composition formingthe energy-absorbing polyurethane ply comprises a mixture of ComponentsA, B and C, described below.

    ______________________________________                        Equivalents                        NCO   OH     Wt %    ______________________________________    Component A:    urea modified monomer mixture of                          1       --     --    3-isocyanato-3,5,5-trimethyl-    cyclohexane isocyanate    [NCO content is about 31.5% by weight]    Component B:    polytetramethyleneglycol, MW 1000*                          --      0.35   --    1,4-butanediol        --      0.45   --    polycaprolactone triol**                          --      0.20   --    Component C:    dibutyl tin dilaurate --      --     0.02    sheeting agent        --      --     0.05    stabilizer            --      --     0.50    ______________________________________     *sold as Polymeg 1000 by the Quaker Oats Co.     **sold as NIAX 301 by Union Carbide.

A glazing laminate is manufactured from this sheet and the propertiesthereof presented in Table I below.

EXAMPLE 8

A multi-ply sheet having a 0.31 mm thick self-healing thermoset ply anda 0.48 mm thick energy-absorbing polyurethane ply is prepared accordingto the method described in Example 4 above, except that the compositionforming the energy-absorbing polyurethane ply is described in Example 7,above.

A glazing laminate is manufactured from this sheet and the propertiesthereof presented in Table I below.

EXAMPLE 9

A multi-ply sheet having a 0.16 mm thick self-healing thermoset ply anda 0.66 mm thick energy-absorbing polyurethane ply is prepared accordingto the method described in Example 4 above, except that the compositionforming the energy-absorbing polyurethane ply comprises a mixture ofComponents A, B and C, described below.

    ______________________________________                        Equivalents                        NCO   OH     Wt %    ______________________________________    Component A:    urea modified monomer mixture of                          1       --     --    3-isocyanato-3,5,5-trimethylcyclohexane    isocyanate    [NCO content is about 31.5% by weight]    Component B:    polytetramethyleneglycol, MW 1000*                          --      0.35   --    1,4-butanediol        --      0.55   --    polycaprolactone triol**                          --      0.10   --    Component C:    dibutyl tin dilaurate --      --     0.02    sheeting agent        --      --     0.05    stabilizer            --      --     0.50    ______________________________________     *sold as Polymeg 1000 by the Quaker Oats Co.     **sold as NIAX 301 by Union Carbide.

A glazing laminate is manufactured from this sheet and the propertiesthereof presented in Table I below.

The following examples demonstrate the reduction in the energy-absorbingproperties per unit thickness of energy-absorbing polyurethane ply inbilayer laminates of the present invention which include externaladhesion promoters.

EXAMPLE 10

A multi-ply sheet having a 0.32 mm thick self-healing thermoset ply anda 0.42 mm thick energy-absorbing polyurethane ply is prepared accordingto the method, and using the compositions, described in Example 4 above.A glazing lamiante is prepared as described in Example 4 except that thesurface of the glass sheet to be contacted with the multi-ply sheet iscoated with a silane adhesion promoter. The properties of the resultinglaminate are presented in Table I below and show a marked decrease inenergy-absorbing properties in comparison to the laminate of comparableply thicknesses and identical compositions of Example 6 above.

EXAMPLE 11

A multi-ply sheet having a 0.46 mm thick self-healing thermoset ply anda 0.56 mm thick energy-absorbing polyurethane ply and glazing laminateprepared from said sheet are prepared as in Example 10, above, and theproperties thereof presented in Table I below. The greater than 1 mmthick sheet results in a laminate having acceptable energy-absorbingproperties despite a high adhesion value.

The following example demonstrates the marked reduction inenergy-absorbing properties of the present laminates which include anenergy-absorbing polyurethane ply prepared by solution casting.

EXAMPLE 12

A multi-ply sheet having a 0.19 mm thick self-healing thermoset ply anda 0.53 mm thick adhesive polyurethane ply is prepared according to themethod, and using the compositions, described in Example 4, above,except that the adhesive ply is formed by the successive casting andevaporation of a solution of polyurethane prepared by solutionpolymerization. The properties of the glazing laminate prepared fromthis sheet are described in Table I below.

EXAMPLE 13

A multi-ply sheet having the ply thicknesses of Example 4, above, isprepared according to the method, and using the composition of Example4, above, except that the overlying adhesive polyurethane ply ispolymerized at about 60° C. for about 20 hours. The properties of theglazing laminate prepared from this sheet are presented in Table Ibelow.

                                      TABLE I    __________________________________________________________________________                    IMPACT RESISTANCE           ADHESIVE ECE R 43 TESTS  SCRATCH ABRASION    EXAMPLE           STRENGTH       227 g ball                                    RESISTANCE                                            RESISTANCE    NO.    (daN/5 cm)                 (psi)                    2.26 kg ball                          -20° C.                               +40° C.                                    Erichsen (g)                                            (% haze)    __________________________________________________________________________    1      10    11.4                    12 m  12 m 11 m 32 g     0.94%    2      11    12.6                    10 m  13.5 m                               13.5 m                                    25 g    1.2%    3      11    12.6                    8 m   11 m 11 m 35 g    1.2%    4      10    11.4                    8 m   11 m 13 m >20 g   <4%    5      10    11.4                    3.5 m  9 m  9 m "       "    6      10    11.4                    4.5 m 10 m 13 m "       "    7       4     4.6                    3 m    8 m  8 m "       "    8       3     3.4                    4.5 m 10 m 12 m "       "    9       3     3.4                    9 m   13 m 13 m "       "    10     20    22.8                    3.5 m --   --   "       "    11     20    22.8                    8 m   11.5 m                               13 m "       "    12      8     9.1                    3.5 m  4 m  3 m "       "    13     --    -- 6 m    6 m 13.5 m                                    "       "    __________________________________________________________________________

Discussion of Laminate Properties

The glazing laminates of Examples 1 through 13 exhibit adhesive bondswhich are moisture resistant and do not delaminate, form bubbles orexhibit any irreversible defects after being subjected to thetemperature and humidity conditions of ANSI-Z26 Test Nos. 3 and 4. Theglazing laminates of the examples exhibit little or no change in theiradhesive strengths measured about 48 hours after the completion of thetests.

All of the laminates exhibit scratch resistant properties of greaterthan 20 g, as measured by the Erichsen apparatus. The laminates ofExamples 1, 2 and 3 comprise monolayer polyurethane plies and exhibitabrasion values of less than 1.5% and scratch resistant propertiesgreater than about 25 g. Furthermore, at Erichsen load values equal toor less than its scratch resistant levels, the indentations formed inthe polyurethane surface by the Erichsen stylus disappear within aperiod of time of about one or two seconds to about several hours, forexample, less than about 20 hours. The laminates of Examples 4 through13 possess an exposed ply of self-healing material in which deformationsdisappear within less than about 10 minutes.

The laminates of Examples 1 to 4, 6, 8, 9 and 11 have energy-absorbingproperties which comply with the requirements of ANSI-Z26 Test Nos. 9,17 and 26 and ECE Regulation No. 43 Test Nos. 4.2 and 4.3. Examples 5,6, 7 and 8 demonstrate the relationship between energy-absorbing plythickness and energy-absorbing properties of a bilayer glazing laminate.Examples 5 and 6 utilize the identical energy-absorbing polyurethane butdiffer in the thickness of the ply: the ply of Example 5 is 0.29 mmthick and does not comply with the R-43 standards, while the ply ofExample 6 is 0.42 mm thick and passes the R-43 tests. A similarcomparison is possible between Examples 7 and 8 where an increase inenergy-absorbing ply thickness from 0.39 mm to 0.48 mm results in alaminate passing the R-43 impact tests.

Examples 10 and 11 demonstrate the relationship of adhesion andenergy-absorbing properties of the present laminate. The higher adhesivestrength possessed by the laminate of Example 10 results in a reductionin impact resistance per unit thickness of the energy-absorbing ply.Example 11 shows that a thicker energy-absorbing layer can result inadequate energy-absorbing properties despite a high adhesive value.

The adhesive ply in Example 12 is formed by solution polymerization andcasting and does not exhibit energy-absorbing properties sufficient tocomply with the R-43 standard at a ply thickness of 0.53 mm.

The adhesive ply in Example 13 is formed by polymerization at 60° C. for20 hours and does not possess the desired low temperatureimpact-resistant properties required to pass the R-43 standard.

The sheets and laminates of Examples 1 to 13 have the optical propertiesas required for their use in automotive safety glass in compliance withANSI-Z26 standards. The sheets and laminates of Examples 1 to 4, 6, 8, 9and 11 possess properties which comply with Safety Standard No. 205,Glazing Materials [49 CFR 571.205, as amended Nov. 16, 1983], andtherefore may be used in vehicle safety windshields in the UnitedStates.

We claim:
 1. A method for preparing a glazing laminate comprising:(1)providing a horizontally supported preformed sheet by forming on ahorizontal support a liquid film comprising a solvent-free mixture ofmonomers capable of forming a polyurethane and a polyurethane-formingcatalyst; (2) maintaining said liquid film at a temperature and for atime sufficient to permit the formation of a uniformly thick and levelfilm; (3) raising the temperature of said uniformly level liquid filmand maintaining the film at an elevated temperature sufficient to fullypolymerize the film into a solid polyurethane sheet within less thanabout one hour while it is positioned on said horizontal support; (4)removing said solid polyurethane sheet from said horizontal support; (5)contacting one surface of a glass or rigid plastic ply with the surfaceof said sheet opposite the surface formed in contact with saidhorizontal support, thereby forming an assembly; and (6) treating saidassembly at elevated temperature and pressure.
 2. A method according toclaim 1 wherein said horizontal support is coated with a release agent.3. A glazing laminate comprising a preformed sheet including anenergy-absorbing polyurethane ply adhered to a glass or rigid plasticply wherein the adhesion between said preformed sheet and said ply isgreater than about 2 daN/5 cm and less than about 15 daN/5 cm, saidpolyurethane ply being prepared by reactive casting, on a levelhorizontal support, a reaction mixture including: an isocyanatecomponent, having a viscosity of less than 5000 mPaS at 40° C., andcomprising an aliphatic diisocyanate, a cycloaliphatic diisocyanate oran isocyanate prepolymer; and, a polyol component comprising a polymericdiol having a MW of about 500 to about 4000, and a short chain diol. 4.A glazing laminate according to claim 3 wherein said ply ofenergy-absorbing polyurethane is greater than or about 0.4 mm thick. 5.A bilayer glazing laminate according to claim 3 wherein said sheet isadhered to a glass ply.
 6. A bilayer glazing laminate which exhibitsoptical, energy-absorbing, moisture and temperature resistant, andabrasion resistant properties as required by ANSI Z26, Test Nos. 1, 2,3, 4, 9, 12, 17, 26, and 28 comprising a preformed sheet according toclaim 3 adhered to a glass or rigid plastic ply.
 7. A bilayer glazinglaminate according to claim 6 wherein said preformed sheet hasself-healing properties.
 8. A safety windshield according to claim
 7. 9.A glazing laminate comprising a glass or rigid plastic sheet and apreformed transparent energy-absorbing polyurethane ply having surfaceproperties including a scratch resistance of greater than 20 g asmeasured by the Erichsen 413 apparatus and an abrasion resistance ofless than 4% haze as measured according to ECE Regulation No. 43, saidpolyurethane ply being prepared by reactive casting, on a levelhorizontal support, a reaction mixture including: an isocyanatecomponent, having a viscosity of less than 5000 mPaS at 40° C., andcomprising an aliphatic diisocyanate, a cycloaliphatic diisocyanate oran isocyanate prepolymer; and, a polyol component comprising a polymericdiol having a MW of about 500 to about 4000, and a short chain diol.